#define _CRT_SECURE_NO_WARNINGS  1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */


bool isUnivalTree(struct TreeNode* root)
{
    if (root == NULL)
        return true;

    if (root->left && root->left->val != root->val)
        return false;

    if (root->right && root->right->val != root->val)
        return false;

    return isUnivalTree(root->left) && isUnivalTree(root->right);
}